Since the EU Scientific Steering Committee stated their report on a risk of infection of bovine infectious diseases, such as bovine spongiform encephalopathy (BSE), to human being, use of meat-and-bone meal of BSE-infected cows as livestock feed has been acknowledged as a problem. In addition, issues of fake brand for branded beef and disguise of other meat to beef have raised awareness of general consumers.
At the same time, in patients with food allergy, various allergic symptoms, such as asthma, dermatitis, gastrointestinal dysfunction, and anaphylactic shock, are caused by food allergens contained in food. In some cases, the symptoms are serious. There is a tendency of an increase in number of food allergy patients, and consumers are highly interested in food safety.
As typical examples of food containing food allergens, generally well known are grain (e.g., buckwheat and wheat), eggs, meat (e.g., beef, pork, and chicken), fishes (e.g., mackerel and sardine), milk, shellfishes (e.g., crab), mollusks, beans (e.g., peanut and soybean), fruits (e.g., mango), and vegetables (e.g., garlic). Such food allergy-inducing food contains food allergy-inducing ingredients such as gluten, gelatin, casein, ovalbumin, ovomucoid, lysozyme, α-lactoalbumin, or β-lactoglobulin. Processed food contains many kinds of food and many kinds of food allergens, but currently there is no way to conveniently detect them.
In addition, in processed food (for example, by heating, pressurizing, enzyme treatment, freezing, drying, or salting), the protein ingredients in the food are denatured in their molecular structures or molecularly modified by the treatment. Therefore, in order to conveniently detect these ingredients in processed food, it is important to use appropriate antigens and epitopes for corresponding processed ingredients and non-processed raw ingredients, and researches and studies therefor have been conducted.
For example, a detection reagent that has been developed as a detection reagent for detecting a material in a sample, such as canned food or livestock feed, derived from animal tissue, represented by cow, hog, and chicken, heat-treated at a high temperature such as a temperature of higher than 100° C. includes a labeled antibody that is an antibody against serum albumin in a material derived from animal tissue heat-treated at a temperature not lower than 120° C. or its antigen-binding fragment labeled with a labeling agent and includes a carrier having a detection region where an antibody against serum albumin in a material derived from the animal tissue or its antigen-binding fragment is fixed. That is, it has been found that an antibody produced by an animal immunized with heat-denatured serum albumin protein as an immunogen specifically recognizes heat-denatured serum albumin and does not have a cross-reactivity with non-heated serum albumin, and proposed is a method (including immunochromatography) for detecting the presence of a heat-treated material derived from animal tissue in a sample (see Patent Literatures 1 and 2).
In addition, an IgE (immunoglobulin E) antibody obtained by immunizing an animal with a mixture (protein) of food allergens composed of non-denatured and/or denatured materials and a method of detecting a food allergen and food allergy-inducing food with the antibody are known (see Patent Literature 3).
Furthermore, it is known that pork in heat-treated food can be detected by ELISA (an immunological measurement method) using a monoclonal antibody produced by a deposited specific cell line (a cell line obtained by immunizing an animal with a specific protein in heated pork) (see Patent Literature 4).
Since this detection method uses a monoclonal antibody produced by a specific cell line (a cell line obtained by immunizing an animal with a specific protein in heated pork), the detection is accurate. However, the preparation of the monoclonal antibody is expensive, and, therefore, it is not suitable for applying to many patients in the medical field.
The present inventors performed a similar experiment by immunochromatography using a polyclonal antibody instead of the monoclonal antibody. The results showed insufficient accuracy due to cross-reactivity with materials other than pork, such as beef, in heated food.
Thus, it was observed that non-specific reaction occurred when pork in heated food, the object to be detected in a sample, was detected by immunochromatography using a polyclonal antibody. Therefore, there still remained a problem that non-specific reaction could not be sufficiently inhibited.
In addition, it is known that a surfactant such as TWEEN 20 or an inorganic salt such as sodium chloride is contained in a diluent that is used for diluting a sample when anallergen (protein) in food is detected by immunological measurement (see Patent Literature 5).